High-voltage fuse having helically wound fusible element and support for helically wound fusible element

ABSTRACT

A pin-wheel-like support for helically wound fusible elements of high-voltage fuses is formed by a pair of coaxially arranged terminal plugs fixedly spaced by a center post of electric insulating material to which a plurality of angularly displaced plates of electric insulating material is affixed.

[ Nov. 26, 1974 United States Patent Kozacka HIGH-VOLTAGE FUSE HAVING 3 571 775 Kmacki 3.680.019 7/[972 Kozacka HELICALLY WOUND FUSIBLE ELEMENT AND SUPPORT FOR HELICALLY WOUND F USIBLE ELEMENT Primary Evumincr-J. D. Miller [75] Inventor: Frederick J. Kozacka, South Hampton,

Assistant ExaminerFred E. Bell Attorney, Agent. 0r-FirmErwin Salzer [73] Assignee:

[22] Filed:

ABSTRACT us. 337/1614337/293 1A piin-whellike SUPP hllcally Wound fusible 52 lSll 1m. 0. elements of high-voltage fuses f rm si by a P of 1 H0lh 85/04 337/161, 186 208 coaxially arranged terminal plugs fixedly spaced by a center post of electric insulating material to which a plurality of angularly displaced plates} of electric insulating material is affixed.

'Field of Search ,231, 337/233, 292, 293

[56] References Cited UNITED STATES PATENTS 3,243,552 3/1966 Mikulecky 337/293 4 Claims, 4 Drawing Figures PATENTE HUVZS I974 FIG. 2

HIGH-VOLTAGE FUSE HAVING HELICALLY WOUND FUSIBLE ELEMENT AND SUPPORT FOR HELICALLY WOUND FUSIBLE ELEMENT BACKGROUND OF THE INVENTION Supports for helically wound fusible elements of high-voltage fuses may be made either of ceramic materials, or materials evolving gases when exposed to the heat of electric arcs. Supports of ceramic materials are generally star-shaped in cross-section. Such supports ought to be made of high-grade ceramic materials, e.g., alumina ceramics, and are, therefore, relatively expensive. Another drawback of supports made of ceramic materials resides in the fact that suchsupports have large surfaces on which metal vapors results from vaporization of fusible elements have a tendency to condense, thus forming a conductive surface layer on the support. Supports made of materials evolving gases when exposed to the heat of electric arcs and having more or less the same geometrical configuration as supports made of ceramic materials share, in part, the disadvantages of the latter, and in part the advantages thereof. v

US. Pat. No. 3,680,019 to Frederick J. Kozacka, issued July 25, 1972 for HIGH-VOLTAGE FUSE HAV- ING A PLURALITY OF FUSE LINKS WOUND HE- LICALLY AROUND AN INSULATING MANDREL shows a support for helically wound fusible elements of high-voltage fuses which is unconventional and lends itself to be fabricated of materials evolving gases when exposed to the heat of electric arcs. According to the above patent the terminals of a high-voltage fuse are in the form of metal cylinders plugging the axially outer ends of a tubular casing, or fuse tube, and the axially inner end surfaces of these cylinders, or terminal plugs, are provided on the axially inner end surfaces thereof with grooves intersecting at right angles. These grooves are engaged by the axially outer ends or edges of four separate plates of electric insulatingmaterial which form spacers for the terminal plugs and further form a mandrel around which a fusible element, or elements, may be wound helically.

It is the principal object of this invention to improve the fusible element support structure shown in the above patent, and more particularly to provide a fusible element support structure of increased dimensional stability, not requiring grooving of the axially inner end surfaces of the terminal plugs. The grooving of the terminal plugs is not only relatively expensive but makes it more difficult to seal the casing or fuse tube by the terminal plugs in such a fashion as to preclude any escape of products of arcing. 1

SUMMARY OF THE INVENTION A fusible element support embodying this invention includes a pair of coaxially arranged, axially spaced terminal plugs, a center post of electric insulating material extending from one of said pair of terminal plugs to the other of said pair of terminal plugs, fixedly spacing said pair of terminal plugs, a plurality of angularly displaced.

plates of electric insulating material having radially BRIEF DESCRIPTION OF THE DRAWINGS FIG. I shows a fuse for elevated circuit voltages embodying this invention along the section 1-] of FIG.

FIG. 2 is a transverse section of the structure of FIG.

FIG. 3 shows a modification of the fuse shown in FIGS. 1 and 2 in the same fashion as FIG. 2; and

FIG. 4 is a top-plan view of the fuse structure shown in FIG. 1.

DESCRIPTION OF PREFERRED EMBODIMENTS In the drawings numeral 1 has been applied to indicate a tubular casing of electric insulating material, e.g., melamine-glass-cloth. Casing or fuse tube 1 is closed at the ends thereof by a pair of metallic terminal plugs 2 press-fitted into it and firmly held in position by steel pins 2a which are arranged radially and project through casing 1 into terminal plugs 2. Each terminal plug 2 is provided with a blind hole, or blind bore 3 in the center of its axially inner end surface. The axially outer ends of a center post 4 engage blind holes, or bores 3 in terminal plugs 2, and thus the former forms a spacer for terminal plugs 2. FIG. 1 shows for reasons of clarity a gap formed between blind holes 3 and center post 4. Actually center post 4 has cylindrical ends which are press-fitted into blind holes 3. Reference numeral 5 has been applied to indicate a plurality of angularly displaced plates of electric insulating material. The number of said plates 5 is preferably 4, and plates 5 are preferably of glass-cloth-melamine evolving relatively large amounts of nitrogen when exposed to the heat of an electric arc. Plates 5 have radially outer ends and radially inner ends. The latter bound or define a prismatic space wherein center post 4 is housed. The I radially inner ends of plates 5 are affixed to center post 4 by fastener means 9, e.g., rivets, (not shown in FIG. 1 but shown in FIGS. 2 and 3) projecting transversely through plates 5 and center post 4. A pair of fusible elements 6 in form of perforated ribbons of sheet silver is wound helically around the radially outer edges of plates 5. The ends of fusible elements 6 are conductively connected at 7 to terminal plugs 2, preferably in the way more fully disclosed in US. Pat. No. 3,571,775 to Frederick J. Kozacka et al., issued Mar. 23, 1971 for HIGH-VOLTAGE FUSE HAVING A PLURALITY OF HELICALLY WOUND RIBBON FUSE LINKS. Casing or fuse tube 1 is filled with a pulverulent arcquenching filler 8, preferably quartz sand.

In the structure disclosed in the above-referred-to US. Pat. No. 3,680,019 the insulating members which support the helically wound fusible element, or elements, are supported only at their axiallyouter relatively short edges, and for this reason this structure is limited to relatively short fuses having a relatively low voltage rating. In the structure which has been described above the plates 5 supporting fusible element 6 on their radially outer edges are supported at their radially inner relatively long sides by center post 4 which imparts considerable dimensional stability to the present structure, and allows its use in connection with relatively long fuses having relatively high voltage ratings.

As shown in FIG. 3 the center post 4 is formed by a length of cylindrical tubing circular in cross-section, e.g., of melamine-glass-cloth. The radially inner ends of plates engage substantially tangentially the outer surface of said length of tubing. The support for fusible element 6 shown in the FIG. 3 includes a first pair of parallel plates 5 and a second pair of parallel plates 5 arranged at right angles to said first pair of parallel plates. The radially inner ends of said first pair of plates 5 and the radially inner ends of said second pair of plates 5 form a four-sided prism whose cross-section is square, substantially tangentially engaging the outer surface of said length of tubing. First fastener means 9 project transversely through the aforementioned first pair of plates 5 and center post 4 formed by a length of tubing, and second fastener means 9 project transversely through the aforementioned second pair of plates 5 and the center-post-forming length of tubing.

FIG. 2 shows that the portions of the center post 4 engaged by plates 5 may be planar rather than cylindrical as shown in FIG. 3. Even if the portion of center post 4 outside of blind holes or recesses 3 issquare in cross-section, the portions or ends of center post 4 entering into recesses 3 ought to be cylindrical, as previously stated.

When assembling a fuse as described above and shown in the drawings, first a sub-assembly is made including parts 4,5 and 9. Thereupon the ends of part 4 are inserted into recesses 3 in terminal plugs 2. Then fusible elements 6 are wound helically around the radially outer edges ofplates 5, and their ends conductively connected to terminal plugs 2 as shown at 7. This yields a second sub-assembly stage. Now terminal plugs 2 are press-fitted into casing'l and affixed to the latter by steel pins 221. The last step in the process of assembly I consists in filling casing l with filler 8 through an appropriate aperture in one of terminal plugs 2 and there- 7 after closing said aperture as by means of a hex screw 10 shown in FIGS. 1 and 4. I claim as my invention: 1. A support for helically high-voltage fuses including a. a pair of coaxially arranged axially spaced terminal plugs;

b. a center post of electric insulating material extending from one of said pair of terminal plugs to the other of said pair of terminal plugs fixedly spacing said pair of terminal plugs;

wound fusible elements of c. a plurality of angularly displaced plates of electric insulating material having radially outer ends and having radially inner ends, said radially inner ends of said plurality of plates bounding a prismatic space wherein said center post is housed; and

d. fastener means affixing said radially inner ends of said plurality of plates to said center post;

2. A support as specified in claim 1 wherein said center post is formed by a length of cylinderical tubing circular in cross-section, and wherein said radially inner ends of said plurality of plates engage substantially tangentially the outer surface of said length of tubing.

3. A support as specified in claim 2 including a first pair of parallel plates and a second pair of parallel plates arranged at right angles to said first pair of parallel plates, the radially inner ends of said first pair of plates and the radially inner ends of said second pair of plates defining a four-sided prism substantially tangentially engaging the outer surface of said length of tubing, and said support further including first fastener means projecting transversely through said first pair of plates and said length of cylindrical tubing and second fastener means projecting transversely through said second pair of plates and said lengthv of cylindrical tubing.

4. A support for helically wound fusible elements of high-voltage fuses including a. a pair of coaxially arranged axiallyspaced terminal plugs each having a bore in the center thereof;

b. a center post extending from one of said pair of terminal plugs to the other of said pair of terminal plugs and engaging with the ends thereof said bore in each of said pair of terminal plugs;

c. a first pair of parallel plates having radially outer ends and radially inner ends, said radially inner ends being in abutting engagement with the lateral surface of said center post and affixed to said center post; and

d. a second pair of parallel plates arranged at right angles to said first pair of parallel plates and having radially outer ends and radially inner ends, said radially inner ends being in abutting engagement with the lateral surface of said center post and affixed to said center post. p 

1. A support for helically wound fusible elements of highvoltage fuses including a. a pair of coaxially arranged axially spaced terminal plugs; b. a center post of electric insulating material extending from one of said pair of terminal plugs to the other of said pair of terminal plugs fixedly spacing said pair of terminal plugs; c. a plurality of angularly displaced plates of electric insulating material having radially outer ends and having radially inner ends, said radially inner ends of said plurality of plates bounding a prismatic space wherein said center post is housed; and d. fastener means affixing said radially inner ends of said plurality of plates to said center post.
 2. A support as specified in claim 1 wherein said center post is formed by a length of cylinderical tubing circular in cross-section, and wherein said radially inner ends of said plurality of plates engage substantially tangentially the outer surface of said length of tubing.
 3. A support as specified in claim 2 including a first pair of parallel plates and a second pair of parallel plates arranged at right angles to said first pair of parallel plates, the radially inner ends of said first pair of plates and the radially inner ends of said second pair of plates defining a four-sided prism substantially tangentially engaging the outer surface of said length of tubing, and said support further including first fastener means projecting transversely through said first pair of plates and said length of cylindrical tubing and second fastener means projecting transversely through said second pair of plates and said length of cylindrical tubing.
 4. A support for helically wound fusible elements of high-voltage fuses including a. a pair of coaxially arranged axially spaced terminal plugs each having a bore in the center thereof; b. a center post extending from one of said pair of terminal plugs to the other of said pair of terminal plugs and engaging with the ends thereof said bore in each of said pair of terminal plugs; c. a first pair of parallel plates having radially outer ends and radially inner ends, said radially inner ends being in abutting engagement with the lateral surface of said center post and affixed to said center post; and d. a second pair of parallel plates arranged at right angles to said first pair of parallel plates and having radially outer ends and radially inner ends, said radially inner ends being in abutting engagement with the lateral surface of said center post and affixed to said center post. 